Patent Literature 1 discloses a five-axis vertical machining center, as shown in FIG. 1. This prior art machining center includes a bed 13 as a base, a column 15 mounted on the bed 13, a rotary table 35 arranged on a moving body 27 which moves left and right on the bed 13, a spindle head 21 supporting a spindle 25, and a saddle 17 supporting the spindle head 21 so as to be vertically movable in the Z axis direction on the left side face of the column 15. A pair of rails 29a, 29b are provided in the bed 13, and the moving body 27 is provided so as to be capable of reciprocating in the lateral directions on the bed 13 along the rails 29a, 29b. 
In this prior art, the saddle 17 is provided on the left side face of the column 15 to move back and forth in the Y-axis direction, and disposed between the column 15 and the spindle head 21, wherein the spindle head 25 is overhung with a large horizontal distance from the column 15, resulting in a greater structure in order to maintain the machine rigidity and damping performance. Therefore, the whole size of the machine is increased, requiring a larger installation space. In Patent Literature 2 discloses a machine tool having a slanted column configured so as to increase the machine rigidity. However, in the prior art of Patent Literature 2, a moving mechanism, which moves in a top face of a bed, is disposed at a position away from a column, since the movable range thereof is not allowed sufficiently because of obstruction by a column. Therefore, a machining head is overhung so as to reach the position away from the column, resulting in the problem similar to that of the prior art of Patent Literature 1.